Ink drop writing apparatus with data synchronizing means

ABSTRACT

IN AN INK DROP WRITING APPARATUS IN WHICH A RECIPROCATING CARRIAGE CARRIES INK DROP EMITTING APPARATUS, WHICH INK DROPS ARE EMITTED THROUGH AN ELECTRIC FIELD TOWARD PAPER, AND IN FLIGHT ARE DEFLECTED IN ACCORDANCE WITH VIDEO SIGNALS FOR PRODUCING INTELLIGIBLE INFORMATION ON SAID PAPER, MEANS ARE PROVIDED, IN ACCORDANCE WITH THIS INVENTION, FOR INSURING THAT DESPITE VARIABLES, SUCH AS DIFFERENT CARRIAGE START-UP TIME AND ACCELERATION, A UNIFORM LEFTHAND MARGIN IS PRODUCED ON THE PAPER, AND ALSO THAT PRINTING FREE FROM TIMING ERRORS OCCURS.

Jan. 12, RM N 3,555,558

INK DROP WRITING APPARATUS WITH DATA SYNCHRONIZING MEANS Filed Jan. 21,1969 2 Sheets-Sheet l 5O symc \HDEO 52 S\6NAL SIGNAL FUELD SOURCE.IQOUQCE BMTD RE5ERVO\R \8 TRANSDUCER j 22 v CHARGING WASTE PROQ ARTTUNNEL REsERvonz NOW \5 THE TSME 48 INK DROP WRWER GEAR MOTO R BOX 70FQOM 58 62 6ATE589 MOTOR FIG 4 CONTROL 72 so 40 4 76 6 J 6 lie! 5% A 7%El *JLJLJLII H ILILJ JLILJLJLJLJLILI E E.

Al W //v vE/vro/e 74 DA v/o M. SHERMAN By A wrap/v5 Y5 Jan. 12, 1971 p,SHERMAN 3,555,558

INK DROP WRITING APPARATUS WITH DATA SYNCHRONIZING MEANS Filed Jan. 21,1969 2 Sheets-Sheet I F- 90 i7 4 I 8% ARmAeE 87 STOP DATA END POsmoN KDETECTOR 2 DATA g f SOURCE v as I 5mm DATA gitffi DETECTOR 9! 6 59 f5TART 5H \FT 8 B T START OF CARRlAGE CLOCK REGSTER HEADING Sl6NAL emu/m5DECODER TO MOTOR GATES CONTROL f g RES ET COUNTER V 1 Q4 uPDATE eTRoBEESEQ O0 REGASTER CARR E 6 DATA R ET SYNCHROWZER gsfig cuzcurrs DETECTORDATA CHARACTER \eNAL GEN 9 TRANSFER sTRoBE cmcunvb \02 START V DEO To Iaewu C,HARG)NC; cwecuw TUNNEL \04 A06 7 T 25 HO \oo\ HZ 400 Hz, r 20OSOLLATOR I D\\/1DER 1 v Q T RESET CARWAGE 22 PRINT DOS \TION DETECTOR 1/Q2 V Q1 5131 Q uPDATEsTRosE Q n4 H2. 2 I 15%. 1 lNVE/VTOR DA V/D M.Sf/EQMAN By & a

. ff/ M 3/- 5 Patented Jan. 12, 1971 3,555,558 INK DROP WRITINGAPPARATUS WITH DATA SYNCHRONIZING MEANS David M. Sherman, La Grange,Ill., assignor to A. B. Dick Company, Chicago, Ill., a corporation ofIllinois Filed Jan. 21, 1969, Ser. No. 792,271 Int. Cl.G01d.15/18;B41j3/04 US. Cl. 34675 6 Claims ABSTRACT OF THE DISCLOSUREBACKGROUND OF THE INVENTION This invention relates to apparatus forwriting with ink drops which are charged by a video signal and directedthrough an electric field, to 'be deflected in accordance with thecharge, and more particularly to improvements therein.

An ink drop writing apparatus has been developed, wherein ink is appliedunder pressure to a nozzle. The nozzle is vibrated in response to asynchronizing signal which is also used for synchronizing video signals.The vibrated nozzle causes an ink jet, which is emitted therefrom, tobreak up into uniform drops at a distance away from the tip of thenozzle. The rate of such drop formation is determined by the vibrationrate. A means for charging each drop is provided at the location atwhich the ink stream begins to break into drops. This means usually is aconductive tube or cylinder. Video signals are applied between thenozzle and cylinder in response to which a drop assumes a chargedetermined by the amplitude of the video signal at the time that thedrop breaks away from the jet stream.

The drop thereafter passes through a fixed electric field, as a resultof which it is deflected by an amount determined by the amplitude of thecharge on the drop.

At the boundary of the electric field there is positioned a writingmedium upon which the drop falls. Since the deflection of the drop isdetermined by the charge on the drop, the arrangement enables one towrite information with the ink which is carried by the video signal.

The vibrating nozzle is carried by a carriage which is made toreciprocate along a predetermined path while the paper upon whichwriting is to occur is moved in a path which is orthogonal to the pathof the carriage. One of the problems which arose with this apparatus isthat because of variables such as variations in the carriage start-uptime and carriage acceleration, and the presence of data, the paper uponwhich the writing occurred would have an irregular left-hand margin.Thus, the visual presentation of'the results of writing with the ink jetwriter was not commercially acceptable and tended to cause irritation toa reader.

OBJECTS AND SUMMARY OF THE INVENTION An object of this invention is toprovide apparatus whereby an ink jet writing system, of the typedescribed can provide a uniform left-hand margin despite variations incarriage start-up and acceleration. This is achieved by sensing thatdata is available, starting carriage motion, sensing when the carriagereaches a predetermined location spaced from the lefthand edge of thecarriage path of travel which is a sufficient distance to insure thatthe carriage is up to its proper speed, and then permitting writing tocommence. Also logic circuits are provided to sense whether or not thecircuit provide the video signals to the charging tunnel are incondition for providing correct character video signals. If not, a delayis provided to enable this to occur.

The novel features of the invention are set forth with particularity inthe appended claims. The invention will best be understood from thefollowing description when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block schematic drawing ofa prior art ink drop writing system.

FIG. 2 is a schematic drawing illustrating the mechanical arrangementfor writing with the ink drop writer.

FIG. 3 is a schematic drawing showing photocell placement along thecarriage travel path.

FIG. 4 is a block schematic diagram illustrative of an embodiment ofthis invention.

FIG. 5 is a block schematic diagram illustrative of a data synchronizercircuit which is shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic drawingof a presently known arrangement which is shown to alford a betterunderstanding of the invention.

An ink reservoir 10 provides ink under pressure to tubing 12 which isflexible. An electromechanical transducer 14 is usually placed adjacentto or around the tubing. The transducer is driven in response to signalsfrom a source 16. The transducer serves to vibrate and/or compress thetubing 12 in the region of the nozzle 18. This results in an ink jet 20being emitted which, at a short distance downstream, breaks up intodrops 22, which are formed at a rate determined by'the frequency of thevibration. In the region where the stream 20 breaks down into drops, acharging tunnel 24 is provided. This comprises a conductive cylinder towhich video signals from a video signal source 26 are applied. The videosignals establish a field Within the charging tunnel so that the inkdrops which are formed therein assume a charge determined by theamplitude of the video signal present at the time the drop separatesfrom the ink jet.

Downstream of the charging tunnel there are usually placed a pair ofelectrodes 28 which are connected to a field bias source 30. As a resultthere is established between the electrodes a constant electric field.The ink drops, which bear charges in accordance with the video signal,enter this field and are deflected by an amount which is proportional tothe amplitude of the charge. This enables intelligent writing to occuron a writing medium 32, which is moved at some synchronous rate past theelectrodes. Drops which do not bear a video charge are captured by atube or trough 34 Which is judiciously placed at one side so as tocapture these drops. It leads to a waste reservoir 36. The paper movesinto the plane of the drawing whereby its motion, together with thedeflection of the drops, may be used for forming intelligiblecharacters.

In order to write lines of information across a wide sheet of paper, anarrangement such as is schematically represented in FIG. 2 may beemployed. By Way of illustration, the ink drop writer 40 is attached toa traveling nut 42, which is free to move on jonrnally supported leadscrew 44. At the top of the ink drop writer is a nut 46 which is free toslide along a rod 48. Accordingly, as the lead screw 44 is rotated inone direction or the other, the ink drop writer will move in a directiondictated by this rotation along a path parallel to the lead screw.

By ink drop writer is here meant a housing which supports the inkreservoir 10, tubing 12, transducer 14, nozzle and charging tunnel 24.The video and sync signal sources are placed elsewhere and are connectedto the ink drop writer by wires. The function of the deflectionelectrodes 28 is performed by a pair of spaced plates 41 which extendalong the path of travel of the ink drop writer and are placed so thatthe stream of drops pass between them on their way to the paper. Atrough (not shown) identical to the tube 34 is provided which extendsadjacent to the bottom plate.

The paper 50 upon which writing is to occur moves in a directionvertical to the direction of the path of motion of the ink drop writer.A motor 52 has a first shaft 54 extending therefrom to a half sectorgear 56. The motor has a second shaft 58 extending therefrom to a gearbox 60, which functions to reverse the direction of rotation of theshaft 62. This reverse motion is communicated through a shaft 62 toanother half sector gear 64 in which it terminates. The sector gears arecut so that as the motor rotates, the sector gear 56 engages a gear 66atached to one end of the lead screw, to rotate the lead screw 44 sothat the ink drop writer is moved from left to right. When the ink dropwriter reaches the right-hand end of the lead screw, the sector gear 56is disengaged from the gear 66 and a sector gear 64 engages a gear 68 onthe other end of the lead screw. This results in the lead screw beingrotated in the opposite direction thereby returning the ink drop writerto its home position on the lefthand side of the lead screw. Motorcontrol apparatus 70 serves the function of energizing the motor torotate over the interval required for the ink drop writer to make oneround trip path along the lead screw. The motor control then waits untilit receives a signal which enables the motor to again function to causethe ink drop writer to make a round trip path.

FIG. 3 is a schematic drawing which shows the placement of threephotocells for detecting when the ink drop writer has attained threepositions along its path of travel. Photocell 72, in conjunction withthe light source 74, operates to detect when the ink drop writercarriage 40 has reached the home position at the left-hand end of itspath of travel. Photocell 76, in conjunction with light source 78,indicates when the carriage has attained the right hand end of its pathof travel. Photocell 80, in conjunction with its light source 82,indicates when the carriage, after leaving the home position, hasarrived at a location at which it no longer is accelerating but ismoving at a constant speed along its path of travel. It should beunderstood that the placement of the photocells as shown in FIG. 3occurs on the structure shown in FIG. 2, but is not shown in the drawingof FIG. 2 in order to preserve clarity in the drawing.

FIG. 4 is a block schematic diagram illustrative of how this inventioninsures a uniform left-hand margin with the apparatus described. A datasource 84 provides the information which is to be printed by the inkdrop writer. The data source may be any of the known data supply systemssuch as magnetic cores, magnetic tape, or may be keyboard originated orinformation coming over a line. The data source can be renderedoperative to transfer data into a register 86 by a signal from thecarriage return detector 88, which includes photocell 72 and lightsource 74. The data source operation is stopped by a signal from thecarriage end position detector 90, which includes the photocell 76 andlight source 78.

In an embodiment of this invention that was actually built and operated,the data from the source was presented serially and each characterconsisted of eight binary bits. These were entered serially into aneight bit register 86, being shifted by clock signals. A 2 kHz. clocksignal source 87 provided clock signals for the data source 84. Theclock signal source output was also applied to a shift clock source 90,which reshaped the signals so that they were suitable for shifting theeight bit register 86. The output of the 2 kHz. clock signal source isalso applied to a divide by eight circuit, 92. The divide by eightcircuit merely constitutes a counter having an eight count capacity.

The data from the source is arranged so that at the biginning of eachline that is to be written a code is placed which signifies thebeginning of a line of data. This code is identified by decoding gatecircuits 89 labeled as Start of Heading Decoder. These gate circuitsmerely constitute a set of AND gates which produce an output only whenthey sense the presence of the code representative of the beginning of aline of data. This output signal is applied to the motor control 70 toinstruct it to start moving the ink drop writer carriage to the right.The output of the start of the heading decoder is also applied to thedivide by eight counter, 92, to cause it to reset.

The eight bit register contents are transferred in parallel to a databuffer register 94, in response to an update strobe signal. The updatestrobe signal is the eighth count output of the divide by eight counter,92. The contents of the data buffer register are applied to a charactersignal generator circuit 96. This circuit performs the function ofconverting an eight bit code into character representative signals whichin this case is a train of signals suitable for application to the inkjet apparatus for printing. The character signal generator circuit isenabled to transfer out the character signals to a video signal circuit102 only in the presence of a data transfer strobe signal which isreceived from a data synchronizer circuit 98.

The data synchronizer circuits 98, are reset and thus enabled tocommence functioning in the presence of an output signal from thecarriage print position detector 100. This includes the photocell andlight source 80, 82, shown on FIG. 3. This photocell is enabled toproduce a signal when the carriage reaches the position from which itWill travel to the end of its path with no further change in velocity.Also, should the data synchronizer circuit 98 receive simultaneously acarriage print position signal and a signal from the divide by eightcounter, it will delay the provision of a data transfer strobe signalfor a period of 10 microseconds. The reason for this is that the databuffer register is being filled with new data at the time of theoccurrence of the update strobe. Should the data transfer strobe occurduring the interval when the data buffer register is being filled, thecharacter signal generator circuit will function improperly since animproper code signal will be provided to it. The effect of the delay of10 microseconds is negligible on the printed copy. When the speed of thecarriage of the ink drop writer is compared with 10 microseconds, theeye cannot discern the ditference between a character which is printedwithout delay, and one which is printed with delay.

The character signal generator circuit, as previously indicated may beany one of the well known character generator circuits which converts acoded input representatrve of characters to a train of output signalswhich can be used to control the position of an electron beam, in conunction with a television scanning raster deflection of the electronbeam to display characters. The analogy of the mechanical motionsprovided for the ink drop writer to a television type scanning rastermay be seen from the fact that the writing paper moves vertically andthe ink drop writer carriage moves transversely to the paper. Drops fromthe ink drop writer are either permitted to reach the paper or aredeflected into the waste reservoir in response to the presence orabsence of video signals. The circuits required for character generationare essentially the same, except of course allowance is made for thereduced speed of operation of the ink jet printer.

The output of the character signal generator circuit 96 is applied to avideo signal generator circuit which converts the signals received tosignals suitable for application to the charging tunnel. The datatransfer strobe which is the output of the data synchronizer circuit isapplied to the video signal generator circuit 102 which converts to aform suitable for application to the charging tunnel 24.

FIG. is a block diagram illustrating the details of the datasynchronizer circuit 98. A 100 kHz. oscillator 4 applies its output to adivide by 400 counter circuit 106, and as clock signals to a firstflip-flop 108, and a second flip-flop 111. The divide by 400 circuit 106is reset in the presence of a carriage print position detector signal.The output of the divide by 400 circuit 106, consisting of 250 hertzsignals, is applied as one input to a first NAND gate 110, and to asecond NAND gate 112. In the presence of the output from the divide by400 counter 106, with the update strobe signal being absent, then theNAND gate 112 is enabled to apply its output through an inverter 114 toan OR gate 116. The output of the OR gate, which is applied to the Iinput terminal of a JK flip-flop 111, upon the occurrence of the nextclock pulse from the 100 kHz. oscillator, causes the flipflop 111 to bedriven to the state with its Q output high whereupon a NOT Data Transferstrobe signal is obtained from its 6 output. Flip-flop 111 is reset uponthe occurrence of the following clock pulse by virtue of the fact thatits Q output is connected to its K input. With its Q output now beinghigh, this following clock pulse returns the JR flip-flop to its stablestate with its 6 output high.

Should an update strobe signal be provided by the divide by eightcounter 92 at the time of the occurrence of an output from the divide by400 counter l-06, then NAND gate 112 is inhibited from operation byvirtue of the input received from the inverter circuit 118. However,NAND gate 110 is enabled. Its output is applied through an invertercircuit 120 to the J input terminal of JK flip-flop 108. Upon theoccurrence of the next clock input from the 100 kHz. oscillator 104,this flipflop is driven to its set state whereupon the negative goingoutput from the 6 output terminal of the flip-flop 108 is applied,through an inverter 12 2 to the OR gate [116. As in the previous case,the output of the OR gate drives the flip-flop 111 to its set state thusproviding the NOT Data Transfer strobe signal. Flip-flop 108 andflip-flop 111 will both be reset upon the occurrence of the followingclock pulse in view of their respective connections from the Q outputterminals to their K input terminals.

The delay of the data transfer strobe signal which is caused by theintroduction of flip-flop 108 into the circuit which drives flip-flop111 is a one clock interval. The clock interval here is the time betweentwo output pulses of the 100 kHz. oscillator :104, or 10 microseconds.This is sufficient to enable the data buffer register to load up.

The data synchronizer circuit shown in FIG. 5 will function continuouslyto insure that the data buffer register has been loaded with a characterbefore the data transfer strobe is provided.

There has been described above a novel, useful and simple system forinsuring a margin alignment and a freedom from error in printing, in anink drop writing system.

Although particular embodiments of the invention have been described andillustrated herein, it is recognized that modifications and variationsmay readily occur to those skilled in the art and consequently it isintended that the claims be interpreted to cover such modifications andequivalents.

What is claimed is:

1. In an ink drop writing system of a type wherein a source of dataprovides data signals to a means to convert said data signals to videosignals and an ink drop forming mechanism projects ink drops toward awriting medium spaced therefrom means for applying video signals to saidink drops from said means to convert said data signals to video signalsto determine the trajectory of said drops, and there is a carriage meansfor carrying said ink drop forming mechanism reciprocally along a pathfrom a starting position to a finishing position, means for insuringNertical alignment of characters written by said ink drop writing systemat the beginning of a line of characters comprising:

means for detecting when said ink drop forming mechanism reaches itsstarting position and providing a starting signal indicative thereof,

a buffer register having its input coupled to said data signal sourceand its output to said means to convert data signals to video signals,

means responsive to said starting signal to enable the flow of data fromsaid source of data to said buffer register,

means for detecting the first of said data signals to flow from saiddata signal source and providing a heading signal indicative thereof,

means for initiating motion of said carriage means responsive to saidheading signal,

a source of update strobe signals,

means for applying update strobe signals from said source to said bufferregister to enable it to accept data signals from said data source,

means for generating data transfer signals,

means for applying said data transfer signals to said means to convertdata signals to Video signals and to enable transfer of video signals tosaid means for applying video signals, and

means responsive to the presence of an update strobe signal to delay theapplication of a data transfer signal until said buffering register hasbeen loaded with data signals.

2. In an ink drop writing system as recited in claim 1 wherein there isincluded a means for detecting when said ink drop forming mechanismreaches a predetermined position at which its velocity is constant andproviding a write signal indicative thereof, and

means for resetting said update strobe signal source responsive thereto,

said system also including means for detecting when said ink dropforming mechanism reaches its finishing position and providing a stopsignal indicative thereof, and

means for terminating the flow of data signals from said source of datasignals to said buffer register.

3. In an ink drop writing system as recited in claim 1 wherein saidmeans responsive to the presence of an update strobe signal to delay theapplication of a data transfer signal until said buffer register hasbeen loaded with data signals includes a source of clock pulses,

means for generating a data transfer signal responsive to a clock pulsesignal,

a delay means connected to said means for generating a data transfersignal,

first gate means for applying a clock pulse signal from said source tosaid means for generating a data transfer signal to activate it,

means for inhibiting operation of said first gate means in the presenceof an update strobe signal, and

second gate means for applying a clock pulse signal from said source tosaid delay means, for generating a delayed data transfer signal in thepresence of an update strobe signal.

4. In an ink drop writing system of a type wherein a source of dataprovides data signals to a means to convert said data signals to videosignals and an ink drop forming mechanism projects ink drops toward awriting medium spaced therefrom, means for applying video signals tosaid ink drops from said means to convert said data signals to videosignals to determine the trajectory of said drops, and there is acarriage means for carrying said ink drop forming mechanism reciprocallyalong a path from a starting position to a finishing position, means forinsuring vertical alignment of characters Written by said ink dropwriting system at the beginning of a line of characters comprising:

means for detecting when said ink drop forming mechanism reaches itsstarting position and providing a starting signal indicative thereof,

a buffer register,

means responsive to said starting signal for enabling the fiow of datasignals from said data signal source to said buffer register,

means for detecting the first of said data signals to flow from saiddata signal source and providing a heading signal indicative thereof,

means for initiating motion of said carriage means responsive to saidhead signal,

a source of update strobe signals,

means for resetting said update strobe signal source responsive to saidstart signal,

means for enabling said buffer register to receive data responsive tosaid update strobe signals,

means for detecting when said ink drop forming mechanism reaches apredetermined position at which its velocity is constant and providing awrite signal indicative thereof,

means for generating data transfer signals,

means for resetting said means for generating data transfer signalsresponsive to a write signal,

means for enabling said means to convert data signals to video signalsto transfer said video signals to said means for applying signalsresponsive to data transfer signals,

means to detect when said ink drop forming mechanism reaches itsfinishing position and providing a stop signal indicative thereof, and

means responsive to said stop signal to terminate said fiow of datasignals from said source of data signals to said buffer register.

5. In an ink drop writing system as recited in claim 4 wherein saidmeans responsive to said data transfer signals for enabling said meansto convert data signals to video signals to transfer said video signalsto said means for applying video signals includes:

means for delaying the application of a data transfer signal to saidmeans to convert data signals to video signals in the presence of anupdate strobe signal for an interval required to insure that said bufferregister has been loaded with data signals.

6. In an ink drop writing system as in claim 5 wherein said meansresponsive to the presence of an update strobe signal to delayapplication of a data transfer signal to said means to convert datasignals to video signals includes a source of clock pulses, having aninterval between pulses at least equal to the time required to load saidbuffer register,

a first and a second flip-flop circuit each having a first and secondinput and a clock input, corresponding first and second outputs, andassuring a state with one of its outputs high in response to the one ofits two inputs to which an input signal is applied when a clock signalis applied to its clock input,

means for applying clock pulses from said source ,to said first andsecond flip-flop circuit clock inputs, a first and second NAND gate,

means connecting said first NAND gate output to said first flip-flopfirst input,

means connecting said second NAND gate output to said second flip-flopfirst input,

means connecting said first flip-fiop second output to said secondflip-flop first input,

means connectingclock pulses from said source to one input to said firstand second NAND gates,

an inverter circuit having an input and an output connected to an inputto said second NAND gate, and

means for applying an update strobe signal to said inverter circuitinput and O S & 1 i d first NAND gate input whereby said secondflip-flop produces a data transfer signal upon the occurrence of a firstclock pulse and in the absence of an update strobe signal, and producesa data transfer "signal upon the occurrence of a second clock pulsein'th'e presence of an update stro'be signal.

References Cited UNITED STATES PATENTS JOSEPH W. HARTARY, PrimaryExaminer US. Cl. X.R. 1786.6

